Conceptually new device structures accounting for sizable quantum effects will be needed if the downscaling of electronic and magnetic devices is to continue. One of these new concepts consists in merging molecular electronics and spintronics. The interaction between the molecule and the metallic contact is of outstanding importance for those molecular spintronic devices, e.g. if a spin-polarized (SP) state can be stabilized or not. In recent years it became possible with SP scanning tunneling microscopy and spectroscopy (STM and STS) to probe the electronic structure over selected areas of a surface with atomic-scale resolution. I will demonstrate that the density functional theory (DFT) can be used to ascertain the adsorbtion geometry of single cobalt phthalocyanine molecules (CoPc) on metallic surfaces. Furthermore, the calculated electron density provides the possibility to simulate SP-STM experiments and to determine the effects of the metal-moleculeinteraction on the electronic structure of the system. I will show, that the CoPc is a promising candidate to generate a SP current or to sense the spin polarization of the electrons: the two primary requirements to make a spintronic device.